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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a1c0fd6938e56cb551de65c7dad9ac318e05b2d0634f3fe275c5e5482b6ca4af' 
  AND token = 'MC1yEj98WSK8aOSoNZ5JaB2+TTTQpqshEg3csY3ADFc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}